The next-generation multimedia wireless communication system on which active research has recently been done requires a system that is able to process a variety of data, including video, wireless data, etc. out of the initial voice-oriented service.
The orthogonal frequency division multiplexing (OFDM) scheme is a multi-carrier modulation scheme for transmitting data by dividing the frequency band into a plurality of orthogonal subcarriers and is one of core technologies that have been in the spotlight in the next-generation multimedia wireless communication system. The orthogonal frequency division multiple access (OFDMA) is a scheme providing multiplexing of multi-user by combining OFDM with a frequency division multiple access (FDMA), time division multiple access (TDMA) or code division multiple access (CDMA).
In general, control signals are transmitted from a base station to a mobile station or from a mobile station to a base station periodically or whenever an event occurs. The control signal refers to a signal not including a user signal. Hereinafter, downlink refers to transmission from the base station to the mobile station and uplink refers to transmission from the mobile station to the base station. An example of the uplink control signals includes a channel quality indicator (CQI). In general, the mobile station transmits the CQI to the base station periodically in order to report channel quality to the base station.
The uplink or uplink control signals include a variety of kinds. Further, in order to transfer several control signals, the control signals are frequently exchanged between the base station and the mobile station. This is because one control signal includes only one control information. The exchange of the control signals is called control signaling. Frequent control signaling between a base station and a mobile station may have an effect on an overall capacity of a system. Further, if this control signaling is increased, the lifespan of the battery, that is one of the major design restrictions of a mobile station, is shortened.
The control signaling does not have an influence on the data rate. It is therefore necessary to minimize the control signaling so as to increase the capacity.